A Comparative Study on Durability of Symmetrically and Asymmetrically Porous Polybenzimidazole Membranes for High Temperature Proton Exchange Membrane Fuel cells

摘要

In this work two different types of porous polybenzimidazole (PBI) membranes symmetrically and asymmetrically porous membranes were successfully fabricated and tested for high temperature proton exchange membrane fuel cells (HT-PEMFCs) The hexafluoroisopropylidene containing PBI (6FPBI) was used and the symmetrically and asymmetrically porous membranes were prepared by soft-template method with two kinds of porogens; they were dibutyl phthalate and 1-ethyl-3-methylimidazoliumbis(trifluoro-methylsulfonyl)imide ([EMIM][TFSI]) respectively The morphologies of the porous membranes were checked by SEM The physicochemical properties required for HT-PEMFC such as doping level proton conductivity mechanical strength and oxidative stability have been studied The porous structure successfully helps the PBI membranes to uptake more phosphoric acid and increase the proton conductivity about 50 % However the porous structure might cause the problems like acid leakage or fuel crossover To overcome these problems the asymmetrically porous structure were introduced The startup/ shutdown tests (12 h on at 150 °C with 200 mA cm-2 and 12h off at room temperature) and long-term durability tests (720 h at 150 °C with 200 mA cm-2) were conducted The maximum power density of symmetrically and asymmetrically porous PBI membranes was 624 and 616 mW cm-2 at 150 °C respectively In the long-term durability tests the asymmetrically porous structure did significantly reduced the phosphoric acid loss and increased the durability of the fuel cell compared to the symmetrically porous structure

獎項日期	2015 8月 3
原文	English
監督員	Lien-Chung Hsu (Supervisor)